Some electrical lighting units such as LED luminaires can be driven at a lower voltage than a conventional mains AC supply, making low voltage.power distribution feasable in a lighting network.
PoE has been developed for supplying low voltage power from a source such as a PoE switch, to a powered device such as a wi-fi access point or video camera, through the same Ethernet cable that carries signals to and from the device. This greatly simplifies installation of networked devices because only one cable is needed for both power and communication. Power is typically supplied from a PoE switch in common mode over the differential pairs of wires found in Ethernet cables. The IEEE 802.3at-2009 PoE standard permits up to 25.5 W of power to be supplied to the network powered devices. Also, non-standardized PoE schemes have been proposed and implemented hitherto.
There is a growing interest in using PoE technology for networked lighting systems. PoE provides a power efficiency advantage for low voltage DC power lighting systems, for example LED based lighting systems where the LED luminaires are connected by Ethernet cabling to a common PoE switch, because only one central AC/DC conversion is needed at the PoE switch to convert AC mains into a low voltage DC supply that can be supplied through the Ethernet cabling to the luminaires.
However, the luminaires in a lighting network are switched on and off repeatedly, in contrast to PoE systems that provide power to network cameras and wi-fi units, which are usually configured to be always on. It would be desirable to switch off the delivery of power through the network to the luminaires that are not in use in order to minimize the standy power consumed by the inactive luminaires, but without requiring a specially designed lighting network controller for PoE or without individually commisioning the PoE switches.